Astronomers have spent the last five years trying to explain a strange star called KH 15D, which winks on an off, sometimes with eclipses that last 24 hours. One theory is that there was a blob of protoplanetary material orbiting the star, occasionally blocking our view. By looking into historical images of the object, astronomers think they might have a new scenario that better explains their observations. They think it could be a double star system with a disk of material surrounding it and rotating with a wobble. This would explain the unusual eclipses.

Having made the drive up to the "El Capitan" region of exposed rock, NASA's Opportunity rover ground away the surface of part of it with its rock abrasion tool (RAT). It then examined the spot with its alpha particle X-ray spectrometer for five hours, and then swapped in its Moessbauer spectrometer, which will analyze for 24 more hours. After Opportunity transfers this data back to Earth, it will move slightly forward, and grind another spot to gather more data about the formation of this rocky outcrop. Scientists back on Earth are getting closer to understand what could have formed this layered bedrock.

One key to the long-term exploration of Mars will be figuring out how to get plants to grow there in greenhouses - they're natural factories for air and food. Since they evolved on Earth, they have no mechanism for surviving in low pressures, which would be a requirement for off-planet greenhouses; they think they're drying out even when there's plenty of water. One solution might be to biochemically adjust levels of hormones that initiate the drought instinct.

NASA's Spirit rover has discovered an unusual patch of sand in a hollow on its journey to the crater "Bonneville". An unusual pattern of irregular lines and polygons in the soil could indicate the presence of a salty brine. This could mean there's liquid water right below the surface of Mars, which could harbour life - microbes thrive in similar environments on Earth. The rover dug a trench and examined the spot with its array of instruments, which scientists will study intensely back on Earth.

Canadian and NASA scientists have captured details of swirling gas as it hovers above the surface of a neutron star. A massive explosion on the surface of the neutron star illuminated the material long enough for scientists to see normally hidden details, such as its accretion disk - a ring of gas swirling around and into the neutron star. The binary pair is located 25,000 light-years from Earth, and it was tracked by NASA's Rossi X-ray Timing Explorer.

NASA announced today that it has chosen 22 researchers to receive up to four year grants to conduct research into advanced human support technologies. The goal of this research will be to help humans achieve the goal of long-duration space flight, both in low Earth orbit as well as exploration of the solar system. NASA received 122 proposals when it originally announced the grants back in March 2003, and these were peer reviewed by scientific and technical experts before the final 22 projects were selected.

The European Space Agency has selected two teams to carry out the detailed design of the ExoMars rover and its suite of scientific experiments to search evidence of life on Mars. The two teams - Astrium UK and MD Robotics - will develop their plans in parallel to create detailed design concepts for the rover. The final rover should be able to roam around the surface of Mars, dig or drill below the surface, and detect current or past evidence of life. If all goes well, the spacecraft will launch in 2009.

When NASA's Opportunity rover dug a trench into the Martian soil two days ago, it revealed a series of mysteries that scientists back on Earth are still puzzling out. The tiny spherical granules that Opportunity found on the surface with its microscope are also underneath the topsoil, but strangely, these look shiny and polished. Opportunity's next task will be to examine a region of exposed rock which has many of these granules embedded inside to help give scientists a better idea of what they're looking at.

The Hubble Space Telescope has further confirmed the existence of "Dark Energy" - a mysterious force that seems to be accelerating the expansion of the Universe. The giant space observatory examined some of the most distant supernovae ever seen and found that this force seems to have been acting at a constant rate for as far back as astronomers can see. This is good news. If dark energy continued to accelerate, some physicists believe the fabric of the Universe could tear apart in an event called "The Big Rip".

Jupiter's moon Io is depositing a trail of dust particles as it makes its journey around the Sun, and the European Space Agency's Ulysses spacecraft has detected them 500 million km away from the gas giant. The dust streams contain particles no larger than smoke, and they originate from Io's many volcanoes, which are constantly erupting across its surface. One unusual feature about the streams is that they have a period of 28 days, which suggests they somehow interact with the solar wind streaming from the Sun.

Instead of looking directly for Earth-sized planets, it might be easier to just try to find the ring of dust that is the fingerprint of terrestrial planet formation. This is according to a new computer model created by astronomers from the Smithsonian Center and Astrophysics and the University of Utah. Their model predicts that stars with disks will be a little brighter in the infrared spectrum than stars without disks; astronomers should be able to predict the size of its planets just from the brightness of its disk in infrared. The recently-launched Spitzer space telescope should be the perfect tool to measure these disks.

Astronomers from Caltech and Yale University have discovered a distant object that could be nearly as large as Pluto. The planetoid is called 2004 DW, and located in the Kuiper Belt, billions of kilometres from Earth. The team estimates that 2004 DW is 1,400 km across, but it's difficult to tell, because the size estimate comes from its brightness. The reflected light from the Sun, which astronomers call "albedo", depends on the darkness of the object. Other astronomers will try and help pin down the characteristics of 2004 DW.

The European Space Agency's Proba spacecraft imaged the Nasca region of Peru; famous for its giant lines and animal figures. The photos were taken from an altitude of 600 km, and clearly show the straight lines (the animals are too faint to see with this spacecraft). Although the markings were created more than 2,000 years ago, the region is so dry they've barely been weathered. Increased human activity, including roads and farming is starting to have an impact, though, and these satellite photos will help scientists track the changes.

Astronomers spotted the brightest supernova seen in modern times almost 17 years ago, and the Hubble Space Telescope has been keeping tabs on it since its launch. Just last year Supernova 1987A put on a new show when a shockwave from its explosion smashed into a ring of gas that had probably been shed 20,000 years ago. Under the pressure from the shockwave, the gas has started to glow, like a ring of pearls around the centre of the explosion. More hotspots will keep appearing until the entire ring of gas is ablaze as it absorbs the full force of the shockwave.

A Russian Soyuz rocket with a classified government cargo lifted off from the Plesetsk Cosmodrome in far northern Russia. The Molniya-class booster took flight at approximately 0705 UTC (2:05 am EST), marking the first launch this year from the space centre. Details about the military communications satellite weren't revealed, only its name: Kosmos 2405. Russian President, Vladimir Putin was on hand to watch the launch.